A Mechanistic Study of Methyl Parathion Hydrolysis by a Bifunctional Organoclay

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• 作者：Chaim Rav-Acha ; Ludmila Groisman ; Uri Mingelgrin ; Zvi Kirson ; Yoel Sasson ; Zev Gerstl
• 刊名：Environmental Science & Technology
• 出版年：2007
• 出版时间：January 1, 2007
• 年：2007
• 卷：41
• 期：1
• 页码：106 - 111
• 全文大小：124K
• 年卷期：v.41,no.1(January 1, 2007)
• ISSN：1520-5851

文摘

The mechanism for the hydrolysis of methyl parathion(MP) by a bifunctional quaternary-ammonium based long-chained organclay (LCOC) containing an alkylamine (-CH₂-CH₂-NH₂) headgroup was elucidated. The pathway of thecatalytic hydrolysis of methyl parathion by the LCOCwas defined by following the effect of replacing H₂O withD₂O, by replacing the primary amino headgroup by atertiary amino group, and by a detailed mathematicalanalysis of the proposed reaction scheme. A phosphorothioateisomer of MP was formed in the presence of the LCOCas an intermediate reaction product, initially increasing inconcentration and then disappearing. The isotope effectwas minimal and substituting a tertiary amine in the LCOCincreased the rate of MP hydrolysis. A mechanism isproposed in which hydrolysis of MP can proceed via botha direct route (specific base hydrolysis) and through theformation of the isomer which then undergoes specific basehydrolysis more rapidly than the parent MP. The relativeimportance of each pathway is a function of pH with thedirect hydrolysis of MP being predominant at higher pH values(pH > 10) and the isomer intermediate pathway predominating at lower pH values (pH ~8-10).